The present invention relates to a high-frequency heating device, more particularly, to the improvement of the cooling device for high-voltage transformers.
Conventionally, any high-frequency heating device for microwave ovens is provided with a cooling fan for cooling the internal electric parts such as the high-voltage transformer feeding high voltages to the magnetron that oscillates high frequencies. FIG. 3 is a cross sectional view showing a typical cooling device applied to the cooling of a conventional high-frequency heating device. Reference number 1 indicates the machine chamber provided in the lateral part of the cooking chamber. Reference number 2 indicates the high-voltage transformer mounted on the bottom plate 3. Reference numbers 4 and 4 indicate the air-intake slits. Reference number 5 indicates the air blower that feeds external air through the air-intake slits 4 and 4 to cool the high-voltage transformer 2 and blows air against the magnetron 6 for cooling. Reference number 7 indicates the exhaust outlet externally discharging air after cooling both the high-voltage transformer 2 and the magnetron 6. Reference number 8 indicates the control panel provided on the front surface of the microwave oven 9. The cooling device provides such a blower unit 5 having its air-intake direction deviated from that of the air-intake slits 4 and 4, while the air passage between both bends like the symbol. In the conventional cooling device mentioned above, since air flows in series while cooling both the high-voltage transformer 2 and the magnetron 6, the effect of ventilation is significantly disturbed, thus causing the blower unit 5 to lose some of its air blowing effect, and, as a result, such a conventional cooling device cannot effectively cool the high-voltage transformer 2. When using a cooling device such as shown in FIG. 3, the blower unit 5 is operated in such a condition that the air-blowing efficiency constantly remains poor, and yet, external air absorbed from the air-intake slit 4 in front of the high-voltage transformer 2 cannot effectively remove heat from this transformer. Consequently, the high-voltage transformer cannot always be cooled sufficiently, thus making it necessary to use such coils having a substantial diameter in order to properly keep the coil temperature below a specific level, and, as a result, conventional microwave ovens are obliged to use expensive high-voltage transformers as high-frequency heating devices.